Emulsions

Question 1

Explain the polarity of an emulsifier molecule.

Answer 1

Emulsifiers have a large polar (cation/anion) charged head, and a long non-polar tail (hydrocarbon chain).

Question 2

How do emulsifiers prevent the separation of oil and water?

Answer 2

Emulsifiers allow non-polar oil droplets (micelles) to disperse in water soluble components. Polar or ion charged head interacts with water soluble components forming hydrogen bonds or dipole-dipole interactions. Non-polar hydrocarbon tails form dispersion forces with oil components.

Question 3

How does soap remove grease and dirt from clothes?

Answer 3

Water molecules attract the hydrophilic heads of detergent anions, lifting the grease up from the surface. By stirring, the grease forms tiny droplets, forming an emulsion. The oil droplets can then move freely in water.

Question 4

Explain why soap scum forms in water that contains Ca+ ions (hard water).

Answer 4

Ca2+ ions form ionic precipitates with the anion heads of soap. The precipitate is what forms soap scum.